1. Field of the Invention
The present invention relates to a light source module, and in particular to a planar light source device and method of manufacturing the same.
2. The Prior Arts
In general, a side-type planar light source module utilizing light-emitting-diode (LED) as its light source is made by installing a plurality of LEDs on a main-body substrate. Refer to FIGS. 1a and 1b respectively for a side view and a top view of an embodiment of a side-type planar light source module utilizing a wedge-shape light guide plate according to the prior art. Wherein, the side-type planar light source module includes a light guide plate 2 and a plurality of LEDs 10, the light guide plate usually is made by ejection-to-mold of acrylic, and above and below it are disposed respectively a diffusion plate 22 and a reflective plate 24. The main-body substrate is a light strip 12, and the LEDs are provided on a surface of the light strip 12, then the light emitting plane of the light strip 12 is aimed at a light incident plane 20 of the light guide plate 2, so that the light reflected by the reflective plate 24 is scattered by the diffusion plate 22, hereby realizing an uniform planar light source.
Then, refer to FIGS. 2a and 2b for a front view and top view respectively of another light source module according to the prior art. Wherein, a planar light guide plate 4 is utilized, and near its two opposing sides are provided with a light strip 12 and LEDs 10 respectively.
In order to obtain uniform illuminance for the light source module, in general, the surface of the light guide plate is printed with material having reflectivity different from that of the acrylic plate, or a reflection plane of a different angle, namely the reflective plate 24, is formed directly on the surface of the light guide plate, as shown in FIG. 1a. Also, refer to FIGS. 3a to 5b, which shows respectively the front views and top views of the embodiments of three kinds of side-type light source modules according to the prior art. In FIGS. 3a to 3b are shown an ink layer 30 containing light scattering particles and formed by transparent resin are formed on a second surface 18 of the light guide plate 2. In FIGS. 4a to 4b are shown a plurality of roughened blocks 40 formed on the second surface 18 of the light guide plate 2, so that its second surface 18 is a rough surface having indentions and protrusions. And in FIGS. 5a and 5b are shown, the second surface 18 of the light guide plate 2 is cut into a plurality of indentions 50, so that the second surface 18 is of a saw-tooth shape. The three embodiments mentioned above all utilize increased reflection area to achieve uniform light illuminance. Usually, the efficiency of a light source module is proportional to the thickness of the light incident plane 20 of the light guide plate, and evenness of the surface of the light incident plane 20, and frequently, in considering cost, weight, and thickness, efficiency has to be sacrificed to balance the factors mentioned above. Besides, the separation of the light source and light guide plate tends to cause loss of lights, thus reducing light illuminance.
Therefore, presently, the design and performance of a light source module is not quite satisfactory, and it has much room for improvements.